1. D. E. Knuth: The Art of Computer Programming volume 1: Fundamental Algorithms (Addison-Wesley 1968) page x. D. E. Knuth: The Art of Computer Programming volume 1: Fundamental Algorithms (Addison-Wesley 1968) page x.
2. S. Rosen (ed): Programming systems and languages (McGraw-Hill 1967). S. Rosen (ed): Programming systems and languages (McGraw-Hill 1967).
3. P. Naur etal: "Revised report on the algorithmic language Algol 60" Communications of the ACM6 1--17 (1963). 10.1145/366193.366201 P. Naur et al.: "Revised report on the algorithmic language Algol 60" Communications of the ACM6 1--17 (1963). 10.1145/366193.366201
4. G.A. Creak: "Backwards ran sentences until reeled the mind" Sigplan Notices 37#2 23--26 (February 2002) 10.1145/568600.568606 G.A. Creak: "Backwards ran sentences until reeled the mind" Sigplan Notices 37#2 23--26 (February 2002) 10.1145/568600.568606
5. A. Chandor J. Graham R. Williamson: A dictionary of computers (Penguin 1970) page 305. A. Chandor J. Graham R. Williamson: A dictionary of computers (Penguin 1970) page 305.